Trane XV80 gas wont fire

Reply

  #1  
Old 03-06-11, 07:12 AM
Member
Thread Starter
Join Date: Mar 2011
Location: usa
Posts: 14
Received 0 Votes on 0 Posts
Trane XV80 gas wont fire

Have a Trane XV80 gas furnace. Model UD100R9V5K0. The Red light flashes 2 times indicating external lockout retries exceeded.
Watching the cycle I get the slow flashing red led, then fast flash, vent motor starts,
Ignitor glows for a while, then ignitor dims. No gas ever turns on. It goes through this another 2 times and then the red led flashing 2 times.
In monitoring the Molex connector pin 7, I never get the 24vac signal. The first stage pressure switch seems to be doing it's thing. I can jump 24vac to the gas valve and it does click the solenoid open, so I know it's not the valve. I have gas going to the valve and the switch on it is ON.
Anyone have any ideas what can be wrong?
 
Sponsored Links
  #2  
Old 03-06-11, 07:38 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,245
Received 2 Votes on 2 Posts
follow the gas valve wires back and check for 24 v at the control board on the GV wires during the ignitor warm-up period. Code 2 means ignition failure and would not have anything to do with the P/S as there is another code for that system.

Most likely your control board has failed.
 
  #3  
Old 03-06-11, 08:33 AM
Member
Thread Starter
Join Date: Mar 2011
Location: usa
Posts: 14
Received 0 Votes on 0 Posts
So what you're saying is that as long as my vent fan starts up and the ignitor glows, I should be getting 24vac at the Molex pin 7 on the controller board, which is the MVL or hot wire going to the
gas valve along with MV COM pin 7. This means that all the safety switches in the PS1 stage (TCO-a, both FRS, and TCO-b) have passed the tests and sent the signal to HLO on the controller, correct?
 
  #4  
Old 03-06-11, 08:40 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,245
Received 2 Votes on 2 Posts
that is correct. However, like I said, follow the wires back from the gas valve. If they run though a limit or switch ( I don't believe they do, but dont know with out the schematic) check that item to make sure it is closed.
 
  #5  
Old 03-06-11, 09:41 AM
Member
Thread Starter
Join Date: Mar 2011
Location: usa
Posts: 14
Received 0 Votes on 0 Posts
There are 3 wires to the gas valve. MVL MVL COM and MVH. MVL and MVL COM go directly to the circuit board, not through any limit switches. MVH comes out of the pressure switch stage 2, but I'm not to stage 2 yet, so the MVH would have nothing to do with the not firing stage 1, right? So my problem is the controller board. My controller board is CNT03078, which has been replaced by CNT05120 which has also been replaced by KIT15815. Any idea where I can get any of these at a decent price?
 
  #6  
Old 03-06-11, 09:45 AM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 6,245
Received 2 Votes on 2 Posts
YOU ARE CORRECT. No idea at decent price. I get all my trane parts from the trane parts supply house in my area.
 
  #7  
Old 03-06-11, 09:48 AM
Member
Thread Starter
Join Date: Mar 2011
Location: usa
Posts: 14
Received 0 Votes on 0 Posts
Thank you very much for all your quick replies and help. This confirms what I thought whereas a local HVAC person said it was my pressure switch and I never got the 3 flash error code.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: